DC plasma electric arc furnace for processing solid waste, method of processing solid waste, and products formed from DC plasma electric arc furnace

ABSTRACT

A DC plasma arc furnace, a method of co-processing waste and metal, a method of producing energy by processing material using the furnace, and the products produced by the furnace are provided. Metal may be efficiently processed by the furnace via an increased organic content in other feedstock fed into the furnace.

BACKGROUND OF THE INVENTION

Waste disposal using conventional means is energy intensive and oftendoes not result in a suitable reduction in the size or volume of thewaste that is treated. In addition, disposal of waste through means suchas landfills is becoming increasingly more difficult as the worldproduces more waste. Landfills also suffer from being generallyundesirable and potentially contaminating groundwater.

Incinerator systems have been used in the past, but they are notconvenient, as they require extensive air pollution control systems toreduce emissions below regulatory levels and may produce toxicbyproducts.

DC plasma arc furnaces provide a benefit in that they completelydissociate waste material into its individual atomic or molecularelements, but the technology is disfavored because of the large amountof energy necessary to run such a furnace.

In addition to the above, the reuse and recycling of metal in wastepresents processing problems. DC plasma arc furnaces are not used toprocess metals because of the amount of energy required to do so. Blastfurnaces are the current state of the art, as they provide large energysavings over existing DC plasma arc furnaces when it comes to processingmetal. The use of DC plasma arc furnaces to recycle metal is notcurrently considered a viable option because of the large amount ofenergy needed to do so.

Thus, the present inventor set about addressing the problem of how toefficiently process waste and recycle metal.

Unless otherwise noted, all documents referred to herein areincorporated by reference in their entirety.

In addition, unless it is understood otherwise from the context, theterm “furnace” herein is used as shorthand for “DC plasma electric arcfurnace.”

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present disclosure is a furnace configured toprocess metal and waste materials, wherein the furnace is a DC plasmaarc furnace.

Another embodiment of the present disclosure is a method of processingmetal in a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of separatingmetals into their atomic elements using a DC plasma arc furnace.

Another embodiment of the present disclosure is a ship carrying on it atleast one DC plasma arc furnace recited in any of the items above.

Another embodiment of the present disclosure is a method of processingmaterials using a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of processingradioactive materials using a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of increasingthe power output of a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of increasingthe organic content of feedstock fed into a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of preparingmaterial for entry into a DC plasma arc furnace.

Another embodiment of the present disclosure is a method of changing thedistance or angle between functional electrodes in a DC plasma arcfurnace during operation based on the feedstock being fed into thefurnace.

Another embodiment of the present disclosure is an electrode collar thatpermits angular movement of electrodes in a DC plasma arc furnace duringoperation of the furnace.

Another embodiment of the present disclosure is an electrode collar thatpermits horizontal movement of electrodes in a DC plasma arc furnaceduring operation of the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein metal feedstock and a non-metal feedstock areprocessed at the same time in the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a vestibule that serves to remove oxygen and/orother reactive gases from feedstock.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, in which the vestibule provides pressure to push feedstockinto the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a conveyor belt used to provide feedstock to thefurnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, used to process any one or more of waste materials,municipal solid waste, iron ore, radioactive material, organic material,and metal.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the waste material contains from 0% to less than50% metal.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the waste material comprises one or more ofmunicipal solid waste, industrial or household waste chemicals, chemicalweapons, medical waste, radioactive material, infectious or otherwisebiologically hazardous materials, human or animal sewage, soils ormarine sediments excavated or dredged from contaminated sites, recoveredwaste material excavated from landfills, used tires, used oil filters,vegetable or petroleum based oils, oil bearing shale, and high sulfurcoal.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the waste material is 65-100% organic.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein a metal feedstock is at least 50% metal, and may beferrous or non-ferrous, or mixtures of both.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the total feedstock fed into the furnace, notincluding a metal feedstock, is at least 65% organic.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the total feedstock fed into the furnace, notincluding a metal feedstock, is at least 75% organic.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the non-metal feedstock comprises municipal solidwaste and either (1) pelletized sewage sludge; (2) pelletized harborsediment; or (3) quartered tires, or any combination of all three.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein feedstock enters the furnace through more than oneentry point, and non-metal feedstock may enter the furnace through anentry point different than the entry point through which metal feedstockis fed into the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising tubes configured to be present at a levelbeneath the top of the slag layer in the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the tubes are configured to deliver steam to thefurnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a gas exit.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising at least one electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising at least two electrodes.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising at least three electrodes.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the tips of at least one electrode are submerged ina slag bath inside the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein one or more of the electrodes are made frommultiple stacked segments.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a backboard electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the backboard electrode does not generate a plasmaarc.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein one or more of the electrodes are hollow-coreelectrodes.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein organic material and/or metal is fed into thefurnace via a hollow-core electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein municipal solid waste and/or tires are fed into thefurnace by bouncing them off of the backboard electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein a plasma arc is generated between at least two ofthe electrodes.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a slag bath layer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the slag bath layer comprises non-metallicmaterials and/or minerals.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the slag bath layer is 10-18 feet thick, and may bemaintained at such a thickness.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a molten metal layer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the molten metal layer is 18-48 inches thick, andmay be maintained at such a thickness.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the molten metal layer comprises ferrous andnon-ferrous metals.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising collars, which in some embodiments maycircumferentially surround a portion of the part of the electrode thatis located on the exterior of the furnace, and which may be configuredto permit horizontal movement and/or angular movement of the electrodesduring operation of the furnace, and in particular during processing offeedstock.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the collars permit the horizontal movement and/orangular movement of the electrodes at the same time that feedstock isbeing processed in the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the collars utilize air pressure to change theangle of the electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the collars comprise an upper and a lower portion.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein pressure differentials between the upper and lowerportions alter the angle of the electrode.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising sensors monitoring the movement and/or positionof the collar.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising one or more of a titrater, a moisture meter,magnetometer, oven, mass spectrometer, gas spectrometer, Geiger counter,an FTIR spectrometer, a Raman spectrometer, a thermogravimetricanalyzer, a differential scanning calorimeter, an NMR spectrometer, ascanning electron microscope, and an energy dispersive X-ray analyzer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a port located at a level of the slag bathand/or a port located at a level of the molten metal layer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the port is used to sample or obtain materials fromthe slag bath.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a port located at a level of the molten metallayer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the port is used to remove metal from the moltenmetal layer.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising wheels configured to transport the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising a sled configured to tilt the furnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the furnace is portable.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the furnace is two stories tall.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, configured to process from 10-25 tons of metal per hour.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, configured to process from 15-75 tons of inorganic andorganic waste.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, configured to remove metal from the furnace, wherein themetal removed contains at least 75% of a single atomic species of metal.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, configured to produce frit.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising feeding organic matter into the furnace suchthat an organic content of all non-metal feedstock being processed inthe furnace is at least 65% or 75% or 90%.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the organic matter fed into the furnace comprisesone item selected from the group consisting of sewage or harbor sediment(which may be pelletized), yard waste (which may be selected from thegroup consisting of grass, tree limbs, brush, and leaves), and tires(which may be quartered).

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, comprising chopping, shredding, pelletizing, compacting,powdering, or granulating waste material prior to feeding it into thefurnace.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the waste material is municipal solid waste, whichmay be shredded and compacted to a size of, for example, from 10-30inches wide.

Another embodiment of the present disclosure is a furnace, method, ship,or electrode collar according to any of the previous embodiments, asappropriate, wherein the waste material is sewage sludge, which may bepelletized to a size of, for example, 2-3 in².

By feeding the disclosed furnace a feedstock that includes an increasedamount of organic material, it is possible to obtain increased energyproduction, thereby allowing for the unexpected ability to create enoughenergy in the furnace to efficiently process not only metals, includingiron ore and other types of metal, which is typically a very energyintensive and costly process, but also waste materials.

The disclosed processing system may be used to process steel and/orwaste and is based upon thermal reduction using a DC plasma electricarc. Without wishing to be bound by theory, the principle is based uponpassing an electric current through a plasma gas medium that generates aresistance in the plasma to produce extreme heat. Under controlledconditions, the process dissociates the materials introduced into thefurnace, and chemically reactive atoms can be directed to the generationof various commercially viable by-products without the release of anydeleterious materials into the atmosphere or the need to dispose ofpotentially hazardous residues. Even toxic materials, often the resultof chelated bonds between organic and inorganic toxic substances, can bedissociated using the processing system and method herein, and suchsubstances may be beneficially reused in their non-toxic, componentstates most captured in non-leaching, vitrified frit. In addition,radioactive materials may be processed using the furnace and methodsdisclosed herein, as the furnace and methods herein serve to separatethe radioactive materials from other materials present in the materialsfed into the furnace.

The furnace and methods disclosed herein may be used in a conventionalland-based setting. However, the furnace and methods disclosed hereinprovide for a size reduction in the furnace that permits the furnace tobe made smaller than otherwise possible while still providing the sameor greater power output as a larger, conventional furnace. As a result,one or more of the furnaces disclosed herein may be loaded onto, forexample, a container ship, a barge or other ship, or a truck or othervehicle, to provide for a mobile processing center, which may process,for example, solid waste and metal in various locations and then travelto a new location to process waste there.

These and other embodiments will be discussed in more detail in thesections that follow.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a top (crown) view of a DC plasma electric arc furnace.

FIG. 2 is a cut-away frontal view of a DC electric arc furnace.

FIG. 3 is a cut-away side view of a DC plasma electric arc furnace.

FIG. 4 is a cross-sectional view of the front of a DC plasma electricarc furnace mounted on a stand in an operational format.

FIG. 5 is a cut-away side view of the furnace in FIG. 4 in an operatingposition within the framework of a mobile overhead crane.

FIG. 6 is a cross-section of one type of system used to inject steamjust below the surface of the molten slag bath.

FIG. 7 illustrates some of the mechanisms used to control theutilization, operating angle and spacing of the functional electrodes.

DETAILED DESCRIPTION OF THE INVENTION

The waste processing system discussed herein is based upon thermalreduction using DC plasma electric arc. The principle is based uponpassing an electric current through a plasma gas medium that generates aresistance in the plasma to produce extreme heat. The system herein iscapable of generating sustained working temperatures of up to, forexample, 10,000 degrees Celsius (° C.). The very high temperatures atwhich plasma arc systems operate dissociate any substance into itscomponent atoms and create very active ions that promote rapid chemicalreactions. Under controlled conditions, such dissociated, chemicallyreactive atoms can be directed to the generation of various commerciallyviable by-products without the release of any deleterious materials intothe atmosphere or the need to dispose of potentially hazardous residues.It is important to note that even toxic materials, often the result ofchelated bonds between organic and inorganic toxic substances, aredissociated in such a process and are beneficially reused in theirnon-toxic, component states. Radioactive materials are also dissociatedin such a process, and such dissociation and separation fromnon-radioactive components that are also present in the processedmaterials may serve as a useful way to recycle materials that contain orare mixed with radioactive materials.

FIG. 1 shows one embodiment of the present disclosure. In FIG. 1,materials to be processed enter the furnace 1 through the large tubulardevice 10. The tubular device 10 does not need to be tubular, and may beany shape suitable for use in introducing the materials to be processedinto the furnace. In certain embodiments, there may be more than onetubular device 10, each configured for use in introducing a differenttype of materials into the furnace. For example, in certain embodiments,inorganic material may be introduced via one tubular device, while adifferent tubular device is used to introduce organic material into thefurnace. The size of the tubular device 10 is not particularly limited,and may be determined based on the size of the material to be introducedinto the furnace.

In certain embodiments, the materials may be fed via conveyor through anitrogen-pressured vestibule interfaced to the tubular device 10. Thenitrogen-pressured vestibule may serve to provide pressure to push thematerial into the furnace. The nitrogen-pressured vestibule may alsoserve to remove oxygen and other reactive gases from the feedstock. Inaddition, a conveyor belt may run through the nitrogen-pressuredvestibule to assist in the feeding of the materials into the furnace.

The material fed into the furnace is not particularly limited, mayinclude, for example, any one or more of waste materials, municipalsolid waste, iron ore, radioactive material, organic material, andvarious unrestricted types of metal. In certain embodiments, multipletypes of materials are fed into the furnace, either through the sametubular device 10 or via separate tubular devices.

Waste materials as used herein is a generic term that includes anymaterial intended to be disposed of. In some embodiments, the wastematerial does not contain metal, or contains from 0% to less than 50%metal. In certain embodiments, the waste material does not contain over50%, or over 40%, or over 35%, or over 25% metal. Waste materials, andmaterials that may be processed according to the present disclosure,include but are not limited to municipal solid waste, industrial orhousehold waste chemicals, chemical weapons, medical waste, radioactivematerial, infectious or otherwise biologically hazardous materials,human or animal sewage, soils or marine sediments excavated or dredgedfrom contaminated sites, recovered waste material excavated fromlandfills, used tires, or used oil filters as well as vegetable orpetroleum based oils, oil bearing shale and high sulfur coal. In certainembodiments herein, the term “non-metal feedstock” may refer to wastematerials or a feedstock of waste materials.

Municipal solid waste may include, for example, material obtained from alandfill. Municipal solid waste could also be obtained directly frombusiness or household waste containers, transferred to the furnace via,for example, garbage truck or barge. In certain preferred embodiments,the municipal solid waste is not obtained from a landfill. Municipalsolid waste typically contains, for example, at most about 65% organicmaterial. In preferred embodiments, when municipal solid waste ispresent in feedstock, radioactive material is not present in thefeedstock.

Iron ore may include, for example, rocks or minerals in which iron ispresent. Iron ores that may be used within the scope of the presentdisclosure are not particularly limited.

Radioactive material may include, for example, waste from nuclearreactors or radioactive materials to be recycled or separated from othermaterials, such as in warheads or used nuclear reactor components. Incertain embodiments, if radioactive materials are used as feedstock,non-radioactive materials, and in particular non-radioactive organicitems, are not present in the feedstock. In other embodiments, metal maybe co-processed or present in the feedstock in addition to radioactivematerials. In other embodiments, organic items may be present in thetotal feedstock fed into the furnace, in addition to radioactivematerials. In embodiments in which organic feedstock is fed into thefurnace concurrently with a radioactive feedstock, the organic feedstockmay be separately fed into the furnace or may be fed into the furnace inthe same feedstock stream.

Organic material may include, for example, sewage or harbor sediment(which may be pelletized or otherwise properly shaped prior toprocessing in the furnace), yard waste (such as grass, tree limbs,brush, or leaves), or tires (which may be quartered or otherwiseproperly shaped prior to processing in the furnace). With respect toorganic material to be fed into the furnace, it is recognized that wasteseparation technology and impurities present in a material mean that anorganic feedstock may be less than 100% organic. Organic feedstockcontains more organic content than municipal solid waste, whichtypically contains 65% organic materials. Thus, organic feedstock asthat term is used in the present specification means a feedstock thatfrom, for example, 65-100% organic. In certain embodiments, the organicfeedstock is over 65% organic, and in preferred embodiments the organicfeedstock is a feedstock that contains at least 75%, more preferably atleast 80%, more preferably at least 85%, more preferably at least 90%,more preferably at least 95%, even more preferably at least 99%, andmost preferably 100% organic material.

The metal that may be processed may include, for example, ferrous ornon-ferrous materials, or combinations thereof, including the iron orenoted above. Examples include scrap steel, aluminum, gold, silver,titanium, electrum and the like. A metal feedstock may contain noorganic material. In other embodiments, the metal feedstock is at least50% metal, or at least 60% metal, or at least 65% metal, or at least 70%metal, or at least 80% or at least 90% metal, or at least 95% metal, orat least 99% metal.

It was surprisingly found that processing organic material, such astires or pelletized sewage sludge, in addition to municipal solid waste,increased the energy output of the furnace. An increased percentage oforganic content in the feedstock led to an increased energy output ofthe furnace. For example, when the feedstock comprised solely municipalsolid waste having an organic content of about 65%, a 1% increase in thetotal concentration of organic material in the feedstock was found tolead to at least a 1.05% increase in energy output by the furnace.

Processing municipal solid waste, which may have an organic content ofabout 65%, in a DC plasma arc furnace will not provide enough energy toallow the furnace to operate as a power station. However, by addingorganic material to the feedstock and increasing the overall organiccontent of the feedstock, the present inventor found that the powergenerated by the furnace greatly increases. For example, in oneembodiment, when the non-metal feedstock fed into the furnace contains75-80% organic material, the furnace may be used as a local powerstation as a result of the increased energy output. This permits thefurnace to act as a power plant. In another exemplary embodiment, it wassurprisingly found that the extra power generated by the furnace as aresult of the increased organic content of the non-metal feedstock maybe used to facilitate the processing of metals in the furnace. Incertain embodiments, the furnace both processes metal from a metalfeedstock and produces excess electricity as a result of the increasedorganic content of the non-metal feedstock, thus permitting the furnaceto simultaneously act as both a power generator and a metal processingunit. It should be noted that the terms power and electricity as usedherein may be used interchangeably unless the context indicatesotherwise.

Co-processing of metal with waste materials is made possible in part byincreasing the concentration of organic material in the non-metalfeedstock, such that the concentration of organic material in thenon-metal feedstock is greater than 65%. By combining, for example,municipal solid waste with organic material and feeding the combinationinto the furnace, the increased energy output by the furnace means thatless energy is required to co-process metals that may be provided to thefurnace in a metal feedstock. The amount of energy necessary to processwaste materials and metals in the furnace herein is therefore less thanthe amount of energy that would be needed if municipal solid waste, asan example, and metals were processed in separate furnaces. The furnaceand methods disclosed herein therefore provide for a previouslyundisclosed efficient and cost-effective method for processing orrecycling metal using DC plasma arc technology, by processing metalssimultaneously with waste materials having a high organic content.

By increasing the organic content of the non-metal feedstock to atleast, for example, 80%, it is possible in some embodiments to generate40 MW of electricity from a furnace that otherwise would provide only 10MW of energy if municipal solid waste alone were used as a feedstock.

The total feedstock fed into the furnace may comprise one or more of theitems described above. A preferred non-metal feedstock containspelletized sewage sludge, harbor sediment, and/or quartered tires; andin particular may contain any combination of those materials. Anotherpreferred non-metal feedstock contains municipal solid waste and either(1) pelletized sewage sludge; (2) pelletized harbor sediment; or (3)quartered tires, or any combination of all three. Thus, anotherembodiment of the present disclosure is increasing the organic contentof a non-metal feedstock fed into the furnace by adding organic matter,such as the materials noted herein.

The total feedstock fed into the furnace may be provided in one or moredifferent feedstock streams. Each stream of feedstock may comprisedifferent materials and may be fed into the furnace at differentpositions, based on the type of feedstock present in the stream. Forexample, metal feedstock, organic feedstock, and municipal solid wastefeedstock may be mixed and fed into the furnace as a single stream in asingle location, for example via the large tubular device 10.Alternatively, the metal feedstock, organic feedstock, and municipalsolid waste may be fed into the furnace as three separate feedstocks inthree different locations. In such an embodiment, the metal feedstockmay be fed into the furnace at any position suitable to deposit themetal into the molten metal layer; the organic feedstock may be fed intothe furnace via a hollow-core electrode; and the municipal solid wastemay be fed into the furnace via the large tubular device 10. Thefeedstock streams are not limited to such an embodiment, however, andmay be mixed and matched based on the available feedstock or the desiredoutput of the furnace. Similarly, the feedstock streams may be mixed andmatched in terms of where and how they are deposited in the furnace,based on how such feedstock streams will be processed in the furnace.

The manner in which power is generated from the furnace is notparticularly limited. Non-limiting examples of how the power may begenerated include that power may be generated using the syngas producedin the furnace or the heat generated from the furnace.

The material fed into the furnace may be pretreated prior to being fedinto the reactor so as to have a desired density, shape, size, mass, orthe like. Pretreating the material prior to feeding it into the furnacemay also lower the risk of non-uniform degradation in the dry atmosphereabove the interior slag bath. As examples, the material fed into thefurnace may be chopped, shredded, pelletized, powdered or granulatedbefore being fed into the furnace. Municipal solid waste in particularmay benefit from being shredded and compacted prior to being fed intothe furnace. Metals may be shredded prior to addition to the furnace incertain preferred embodiments.

The physical form of the material to be fed into the furnace may bedetermined based on how the form will impact the processing of thematerial. For example, municipal solid waste may be shredded andcompacted into sizes and shapes roughly resembling a basketball, oralternatively shapes that are roughly 25-30 inches wide. Such municipalsolid waste could be fed into the furnace via the tubular device 10. Formunicipal solid waste, the size of the material must be large enoughthat the material will not combust above the slag layer, since municipalsolid waste may contain material that would be dangerous if it combustedabove the slag layer. Thus, it is not recommended to make the municipalsolid waste too small or too light. In addition, the municipal solidwaste must not be so heavy or large that it will not break down in theslag layer before sinking to the molten metal layer of the furnace.Thus, in preferred embodiments, the compacted municipal waste is fedinto the furnace in the shape of a sphere having a diameter of from 10inches to 30 inches. In more preferred embodiments, the diameter is25-30 inches.

On the other hand, some waste material or metals, such as organicmaterials, may be fed into the furnace at a particle size of less than 2cubic centimeters. Such a size with respect to organic material willpermit organic matter to dissociate prior to entry into the slag layer,which is a beneficial outcome. Such dissociation occurs as a result ofthe high heat and high organic content of the material. In an embodimentin which pelletized sewage sludge is used, its size may be 2-3 in² incertain embodiments. In embodiments in which tires are used, the tiresmay be quartered.

When metal is fed into the furnace, the size and shape of such metal isnot particularly limited. The size may range from 1 cm or smaller to 10meters long or longer. For example, items as small as nuts or bolts maybe fed into the furnace, and it is envisioned that if properlypre-processed, items as large as a car may be fed into the furnace.

Material to be fed into the furnace may be pretreated to as to removeexcess moisture. The method of drying or removing excess moisture duringpretreatment is not particularly limited. Excess moisture in thefeedstock could potentially lead to explosions within the furnace.Accordingly, in preferred embodiments, the materials entering thefurnace contain from 0% to less than 20% moisture by volume. In morepreferred embodiments, the materials entering the furnace contain lessthan 15%, or less than 10%, or less than 5%, or less than 1% moisture byvolume. In a most preferred embodiment, the materials entering thefurnace do not contain moisture.

Material to be fed into the furnace may also be pretreated to as toremove excess air. In particular, it is preferred that excess hydrogen,oxygen or other combustible gases be removed from the material. Themethod of removing air during pretreatment is not particularly limited,and such removal may occur via vacuum or compaction in certainembodiments. Such compaction may be such that the material is compactedinto spheres, pellets, or other shapes suitable for processing in thefurnace. In preferred embodiments, the material fed into the reactor isfree from hydrogen, oxygen or other combustible gases. In particularlypreferred embodiments, the material fed into the reactor is free fromair pockets.

The inventor has found that municipal solid waste in particular maybenefit from pretreatment, including shredding and compaction intospheres. In particular, compacting municipal solid waste permits thefurnace to process large volumes of municipal solid waste, higher thanthose previously known.

The four tubular projections 11 from the circumference of the furnace 1are connections via which steam is fed to the furnace. Although thefigure shows four tubular projections 11, the number of tubularprojections is not particularly limited, and may be determined based on,for example, the most efficient way to evenly distribute steam below thesurface of the slag layer.

The shape of the tubular projections 11 is similarly not particularlylimited. In certain embodiments, the steam is fed into the reactor at acontrolled uniform rate. In some embodiments, for example, where onlyorganic feedstock and optionally metal is fed into the furnace, it ispossible that the addition or use of steam is not necessary.

The tubular projections 11 feed steam into the furnace below the surfaceof the interior slag bath. In some embodiments, the steam is fed intothe furnace just below the surface of the slag bath. Steam is fed intothe furnace far enough below the surface of the slag bath to preventsteam from entering the gas portion of the furnace. Because steamcontains oxygen, it could potentially provide for an explosion ifallowed to come into contact with some of the elements in the gasportion of the furnace resulting from processing.

The steam provides both hydrogen and oxygen into the furnace. Inpreferred embodiments, the hydrogen and the oxygen are used during theprocessing of the material in the furnace. For example, the processingof the materials in the furnace may include the degradation of organicmaterial. Degradation of organic materials results in the release offree carbon into the slag bath in the reactor. The free carbonpreferably binds to available oxygen, thereby forming carbon monoxide,which is a combustible gas. The free hydrogen is also combustible andboth gases will vaporize from the surface of the silica bath in certainembodiments.

Gas may exit from furnace 1 via a gas exit. The gas exit on the crown ofthe embodiment shown in FIG. 1 is a capped exhaust 12. The type of gasexit is not particularly limited. In this embodiment, the cap is openedvia a hydraulic unit, allowing for connection to a transitional pipethat may direct the combustible gases to a cogeneration system. Themethod of opening or operating the cap is not particularly limited.

In certain embodiments, some of the nitrogen collected from thecogeneration exhaust can be liquefied under pressure and used as thefurnace coolant. The remaining nitrogen may be used to support the entryof organic and inorganic materials into the furnace (for example, byproviding nitrogen for the pretreatment of the materials to be fed intothe furnace) and/or to provide the required anoxic gas atmosphere insideof the furnace. The nitrogen can be separated from carbon dioxide in thecogeneration exhaust via a specialized ceramic membrane filter unitknown in the art. The specific filter used is not particularly limitedand one such ceramic membrane filter is manufactured by PallManufacturing.

The circular units 13 on line A in FIG. 1 are electrodes. The electrodesmay be made from those materials known in the art. In certain preferredembodiments, the electrodes are carbon or graphite electrodes. One orboth of the electrodes 13 may have portions partially submerged in theslag bath.

The electrodes 13 transport electrical energy and induce the formationof plasma at their tips. The tips of the electrodes may be submerged inthe slag bath, or alternatively may be located at a position just abovethe slag bath.

The electrodes are expendable from the lower end and must be replacedover time. In certain embodiments, the electrodes are made from multiplestacked segments. The stacked segments may be held together by threadedportions, for example by externally threaded male and internallythreaded female couplings. Accordingly, replacing the electrodes mayinclude attaching a new section of electrode to a top portion of theelectrode (which may be the uppermost portion of the electrode outsideof the furnace, where the portion of the electrode closest to the slagbath is considered the bottom of the electrode) and then lowering theelectrode into or further into the furnace. Where the electrode segmentsare threaded together, this may be accomplished by inserting androtating a new electrode segment into the threaded opening at the top ofthe electrode, and this may be facilitated by an overhead cranesupported by an electrode column stand. This has the advantage of makingthe operation of the furnace better, since it is not necessary towithdraw the electrodes from the furnace in order to replace them, noris it necessary to turn off the furnace in order to replace theelectrodes. Instead, the new sections of electrode may simply be addedto the existing electrodes, which may occur during operation of thefurnace. Thus, the furnace may continuously run during the addition ofnew sections of electrode.

Herein, the term “during operation of the furnace” typically meansduring a time in which feedstock is being processed in the furnace.

In certain embodiments, the electrodes can have a hollow-core. Thediameter of the hollow core is not particularly limited, but typicallymay have an opening of up to 18 inches in diameter. The diameter of theopening is large enough to permit the efficient feeding of theappropriate materials into the hollow electrode. Such an electrodestructure allows for materials to be delivered through the hollow coreof the electrode and directly into the plasma or into another part ofthe furnace. In such embodiments, the material is preferably pelletized,powdered, granulated, or otherwise pretreated as previously disclosed.

Hollow-core electrodes may be used as electrodes that generate a plasma,e.g., nitrogen, arc. In alternative embodiments, hollow-core electrodesmay be electrodes that do not generate a plasma arc within the furnace.

The manner and condition in which material may be fed into a hollow-coreelectrode is similar to how material may be fed into the furnace viatubular device 10. For example, feeding material into a hollow-coreelectrode may be accomplished in certain embodiments via anitrogen-charged feeder tube connected to the top one or more, or all ofthe, electrodes. When material is fed into the furnace via a hollow-coreelectrode, the tip of the electrode may be present in the gas portion,slag bath, or molten metal layer in the furnace (when the electrode is anon-functional electrode), depending on where it is desired to depositthe material in the furnace. The tube is preferably easily removable soas to facilitate replacing the electrode or adding a new electrodesegment. In certain embodiments, organic matter and waste material suchas sewage sludge or harbor sediment may be fed into a hollownon-functional electrode which deposits the material in the furnaceabove the level of the slag. In certain embodiments, municipal solidwaste is not fed through a hollow electrode or through a functionalelectrode. In other embodiments, metal may be deposited into the furnacevia a hollow-core electrode.

In embodiments in which the furnace contains more than one electrodes,the electrodes may be either individually the same or different.

The circular unit 14 on line B is a carbon electrode that acts as abacking board to direct the materials entering through the funnel portor feed tube 10 into the slag bath. In this disclosure, such anelectrode is sometimes referred to as a backboard electrode.Accordingly, one embodiment of the present disclosure relates to athree-electrode furnace. In certain aspects of that embodiment, eitherone or two of the electrodes may be non-functional, and thus the plasmaarc may be generated by two or one electrodes, respectively, in thosecertain aspects.

In preferred embodiments, municipal solid waste enters the furnacethrough the funnel port, hits the backboard electrode, and is thusdirected into a predetermined position in the slag bath. The backboardelectrode is preferably configured such that it directs materials intothe slag bath at a position between functional electrodes, for exampleelectrodes 13. In preferred embodiments, the addition of material intothe furnace via the backboard electrode does not disrupt the plasma arc.

In preferred embodiments, metal is fed into the furnace. The metal maybe fed into the furnace at any location suitable to deposit the metalinto the molten metal layer, and in certain embodiments is depositedinto the furnace via a metal feedstock that includes at least 50% metalby mass. In other embodiments, the metal feedstock may include from50-100% metal, for example at least 60%, at least 70%, at least 80%, atleast 90%, or at least 95% metal. In certain embodiments, the metal maybe deposited directly into the molten metal layer. In other embodiments,the metal may be fed into the furnace in the slag layer or in the gaslayer above the slag layer. When the metal is deposited into the furnacein the slag layer or in the gas layer above the slag layer, the metalwill typically fall through the slag layer into molten metal layer. Themetal may be deposited into the furnace via an inactive hollow-coreelectrode, or may be deposited using the backboard electrode. Anypretreatment of the metal or the form in which the metal is fed into thefurnace may have an effect on the proper place at which to insert themetal into the furnace.

Both the funnel port and a hollow electrode may be used to feed materialinto the furnace simultaneously, thereby permitting different feedstockto be fed into the furnace at the same time. For example, municipalsolid waste and tires may be fed into the furnace via the funnel port,while pelletized sewage sludge and pelletized harbor sediment is fedinto the furnace via a hollow electrode, for example the backboardelectrode.

When material that is highly organic, such as sewage sludge, is the onlynon-metal material added to the furnace, a functional electrode may beused to deliver the material. The increased efficiency from such asystem permits for a large size reduction in the furnace, as opposed toa traditional dual electrode system with a separate feeding mechanism ora three-electrode furnace.

FIG. 2 is a cross-section of the furnace shown in FIG. 1A, taken alongline A-A.

The electrodes 13 in FIG. 2 are functional electrodes by virtue ofhaving a plasma arc generated between them. The plasma arc is preferablya nitrogen plasma arc. The electrodes 13 may be located above or in theslag bath, but in preferred embodiments they are located above the slagbath and do not contact the slag bath. Without wishing to be bound bytheory, it is believed that the plasma arc between the electrodes entersthe slag bath. In FIG. 2, functional electrodes 13 are shown to the leftand right of the non-operating electrode 14 (which is non-operating byvirtue of not having a part of the plasma arc contact it) that serves asa backboard to direct substances into the slag bath 15.

The slag bath may include molten silica or other materials that havebeen processed by the furnace. The slag bath may typically be made fromnon-metallic materials, minerals, or impurities in the feedstock, andforms upon the processing of the feedstock. The temperature of the slagbath may be selected based on the materials to be processed in thefurnace. For example, in the case where the material being processed isa complex organic material, it is understood that the most complexorganic materials begin to deteriorate at 1,500° C. Thus, a normaloperating slag bath temperature for the furnace may be from 1,500-4,000°C., or from 2,500-4,000° C., depending upon the material to beprocessed, with a temperature of about 4,000° C. or a temperature of4,000° C. being particularly preferred.

The thickness of the slag bath may vary and may be controlled based onthe feedstock fed into the furnace. For example, iron ore may contain alarge amount of silicate, which may produce more slag than, for example,steel obtained from scrap. Waste such as municipal solid waste does nottypically contain much mineral content, and thus if only municipal solidwaste is fed into the furnace, a thick slag layer may not form. Thethickness or height of the slag bath may be controlled by draining theslag layer. The drained slag layer may be formed into, for exampleconstruction blocks. The drained slag bath may also be deposited intomolds of various shapes, depending on the desired end use of the moldedand cooled slag.

The thickness of the slag bath may be, for example, 10 feet thick orthicker. For example, the slag bath may be 10-18 feet, and may be inparticular 10, 15, or 18 feet thick.

Beneath the slag bath 15 in FIG. 2 is a layer of molten metal 16. Themetal is preferably generated from the metal fed into the furnace.

The ratio of the thickness of the slag bath to the thickness of themolten metal layer may vary and may be controlled based on the feedstockfed into the furnace. For example, iron ore may contain a large amountof silicate, which may produce more slag than, for example, steelobtained from scrap, thus leading to a higher ratio of slag to metal. Incertain embodiments, the ratio of the thickness of the slag bath to thethickness of the molten metal layer may be predetermined or controlledsuch that it is maintained at a predetermined ratio.

In certain embodiments, the molten metal layer 16 is at least 18-48inches thick. In other embodiments, the thickness of the molten metallayer 16 may be at least 24, 30, 36, or 48 inches thick or any subrangetherein. The thickness of the molten metal layer 16 may be configuredbased on the feed rate of metal into the furnace and may be maintainedby draining metal out of the molten metal layer at a predetermined rateor height. The height of the molten metal layer may be maintained at asteady state by removing metal from the molten metal layer at the samerate at which metal is added to the molten metal layer.

The molten metal layer is preferably thick enough to permit the metalsin the furnace to separate into different strata based on atomic weight,with heavier metals sinking to the bottom of the molten metal layer. Inthis way, the furnace may be used as a metal separator, by removingmetal from the molten metal layer at predetermined positions. Forexample, if gold or silver separate out at a certain level in the moltenmetal layer, the furnace may be positioned such that the metal that isdrained from the molten metal layer contains the desired gold or silver.A similar process may be used to specifically extract different desiredmetals from the molten metal layer. Multiple outfeeds may also be usedto selectively remove metal from the molten metal layer.

The molten metal layer 16 may contain both ferrous and non-ferrousmetal. The metal may be removed from the furnace and formed or processedinto an appropriate size and shape depending on the metal's future use.

The functional electrodes 13 shown in FIG. 2 may in some embodimentsproject into the slag bath 15, but do not contact the molten metal layer16 beneath the slag bath 15.

The furnace is preferably lined with special ceramic refractory blocks(an example are those produced by RADEX) that can withstand the hightemperatures. FIG. 2 shows two layers of blocks 17A and 17B at thebottom of the furnace therein, as well as large blocks 17C that surroundboth the slag and molten metal layers. Typically, these blocks maydeteriorate during routine use, and when that happens, the furnace mustbe emptied. For example, it may be necessary to replace the blocks everysix months.

The molten metal layer 16 may in certain embodiments receive electricalenergy via conductors. In the embodiment shown in FIG. 2, the conductorsmay be, for example, located in an interior layer of blocks that are fedby conductors 18, which in this embodiment are illustrated at the edgeof the two rows of blocks 17A and 17B in FIG. 2. The conductors 18 maybe connected to feeder cables via conductors on the base of the furnace.

In a single electrode system, the electrical energy received by themolten metal layer 16 establishes an anode and cathode for a functionalelectrode.

The interior of the furnace may be charged with nitrogen or anotherplasma-suitable gas and, in the case of nitrogen, the nitrogen atoms maybe excited so as to form a plasma. When hollow-core electrodes are used,the hollow cores may also be charged with nitrogen to form a plasma. Thetemperature of the plasma may be set to a predetermined temperature,based on the desired reaction inside the furnace, and can be adjusted upor down based on the amount of energy applied. For example, thetemperature of the plasma can reach 10,000° C. in some embodiments. Thetemperature of the plasma is transferred to the slag bath, and thus thetemperature of the plasma may be used to control the temperature of theslag bath.

The functional electrodes 13 may be held in place on the crown viaspecial collars 19, which in some embodiments may circumferentiallysurround a portion of the part of the electrode that is located on theexterior of the furnace, and which are configured to have severalfunctions. For example, the electrodes deteriorate at a defined rate attheir tips. The collars may include a pressurized fitting that moves theelectrode downward at a preset compensatory rate to keep the electrode'srelative location in the furnace constant, or to move it up or down tocompensate for changes in the slag bath or the molten metal layer. Thecollars may also include sensors therein or be attached to sensorswithin the furnace that determine and control the rate and frequency ofthe electrode lowering and other movements.

The collars 19 also can be adjusted to provide for an appropriate angleof the electrodes. Angling the electrode tips toward each othersignificantly increases convections within the slag bath and for certainmaterials may markedly increases the efficiency of the furnace for theprocessing of, for example, steel, or for the processing of wastematerials.

The collars 19 also provide a unique characteristic of the presentfurnace. In particular, collars 19 are configured to, and provide forthe ability to, move the horizontal space between the electrodes apredetermined distance. Such horizontal movement includes expanding ornarrowing the distance between the functional electrodes 13, which willalter the rate of convection within the slag bath 15. Widening the gapwill diminish convections, and may be suitable for materials processeddirectly through hollow-core electrodes where the energy demand may belower. Conversely, narrowing the gap will increase convections, whichwill result in more uniform temperatures in the slag bath area betweenthe electrodes, where materials fed through the crown vestibule ortubular device 10 will be processed, thus allowing for a more uniformregulation of energy demand. Expanding or narrowing the distance betweenthe functional electrodes 13 allows for further control of the energyused to process materials, and thus allows for a different amount ofenergy to be used based upon the material being processed and itsdensity and/or composition.

By providing for both horizontal and angular movement of the electrodes(in addition to the previously discussed vertical movement—meaningcloser or further from the molten metal layer), the furnace provides forpreviously unheard of control over the processing conditions within thefurnace. Without wishing to be bound by theory, the convection andcurrent flow in the slag layer is controlled by electron flow betweenthe functional electrodes, with closer electrodes providing strongerconvection and current flow and further apart electrodes providingweaker convection current flow.

The electrodes may be moved in three dimensions (e.g., angularly,horizontally, and/or vertically) while the furnace is operating so as tomaximize the efficiency of the furnace. For example, in one embodimentof the present disclosure, a sample of the feedstock is removed andtested prior to entry into the furnace. The tests may include a test ofthe moisture content, gas content, organic content, metal content,radioactivity, or other relevant factors. The testing may be performedby, for example, a titrater, a moisture meter, magnetometer, oven, massspectrometer, gas spectrometer, Geiger counter, an FTIR spectrometer, aRaman spectrometer, a thermogravimetric analyzer, a differentialscanning calorimeter, an NMR spectrometer, a scanning electronmicroscope, an energy dispersive X-ray analyzer, or other suitableapparatus. The vertical, angular, and horizontal positions of thefunctional electrodes may then be altered based on the results of thesample with no interruption to the operation of the furnace. In thisway, different feedstocks may be fed into the furnace and the electrodesmay be positioned accordingly without the need to shut down the furnaceto move the electrodes. Thus, one embodiment of the present disclosureis the horizontal movement of functional electrodes during the operationof the furnace, where such movement may be determined based on the typeof material being fed into the furnace. Another embodiment of thepresent disclosure includes the vertical movement of functionalelectrodes during the operation of the furnace, where such movement maybe determined based on the volume or feed rate of material being fedinto the furnace.

The movement of the electrodes permits for multiple horizontaldistances, angles, and/or heights between the electrodes to be utilizedwithout interrupting the feeding of material into the furnace or theoperation of the furnace. For example, during the uninterruptedprocessing (meaning that the furnace is not shut down during processingof the feedstock; the furnace is not shut down for cleaning, adjustment,or maintenance; or alternatively that the feedstock is continually fedinto the furnace) of a batch of feedstock of various compositions, thefunctional electrodes may be moved horizontally and/or angularly once,twice, three times, four times, or more to accommodate differentcompositions in the feedstock. The furnace is not shut down while thefunctional electrodes are moving, and the furnace may therefore processmaterials while the electrodes are moving. This removes the need fortime-consuming and expensive furnace downtime between differentfeedstocks. For example, the electrodes may be moved during processingto accommodate different materials in the feedstock or different ratiosof municipal solid waste, organic content or waste, and metal present inthe materials fed into the furnace.

FIG. 2 also illustrates two ports 20 and 21. The ports may be used tosample, load, unload, or change the slag or the molten metal. In theembodiment shown in FIG. 2, port 20 is shown with two connections intothe furnace: one that may be used to obtain samples or material from theslag bath; and another that may be used to lower the slag bath levelwithout altering the level of the molten metal layer. Thus, port 20 doesnot contact the molten metal layer. Port 21 is shown with one connectionto the furnace, which allows for sampling of the molten metal and alsoallows for complete emptying of the furnace to facilitate changing theinterior ceramic blocks. Thus, port 21 may be present at a part of thefurnace which permits all liquid to drain from the furnace using port21. It is noted that in the embodiment shown in FIG. 2, port 20 islocated above port 21 with respect to the bottom of the furnace.

FIG. 3 is a cross-section of the furnace shown in FIG. 1A, taken alongline B-B.

This drawing shows the non-functional, or backboard, electrode 14 withthe specialized collar used on the functional electrodes 13.

The backboard electrode 14 does not need to utilize electrical energyand in certain embodiments has a solid core. A portion of the backboardelectrode 14 may be canted at an angle and its length is adjusted sothat its tip will be above the slag bath and just behind the rear planeof the functional electrodes. The backboard electrode 14 deteriorates ata much slower rate than the functional electrodes, and thus may requirereplacement of the canted section only once every six months.

In other embodiments, the backboard electrode 14 is a hollow-coreelectrode, and in those instances may be used to increase the energyratio of the feedstock, for example by permitting the processing of morehighly organic materials as discussed above, for example feedstockscontaining more than 65% organic matter. For example, in embodiments inwhich the backboard electrode is a hollow-core electrode, organic matterhaving an organic content of greater than 75% may be effectively fedinto the furnace, thus increasing the overall organic content of thefeedstock fed into the furnace. Such an embodiment may permit thefeeding of material into the furnace via the hollow-core electrode ofmaterial having an organic content of, for example, from 65-100%. Inpreferred embodiments, the feedstock fed into the hollow-core backboardelectrode may contain 75%, 85%, 95%, or 100% organic content. By feedinghighly organic content into the hollow-core electrode, the overallorganic content of the non-metal feedstock fed into the furnace may beincreased to provide for the disproportionately increased energy outputdiscussed herein.

In certain embodiments, materials to be processed, such as municipalsolid waste or tires, may be driven into the furnace under nitrogenpressure, where they will strike the backboard electrode and be guidedinto the slag bath between the electrodes, which exposes the material tothe area of maximum convection and exposes the material to the mostuniform temperatures in the slag, thereby leading to degradation.

FIG. 3 also shows the ports 20 as well as the port 21 previouslydiscussed. In the embodiment illustrated in this figure, the ports 20are located at and below the tip of the functional electrodes 13.

The interior refractory blocks 17A-B contain materials that conductelectrical energy as previously discussed. FIG. 3 also shows conductors18. In this embodiment, the lower row of blocks 17B is non-conducting,but contains on its upper and lower surfaces insulated conductormaterial that is connected to the conductors 18 and two cableconnections 22 on the base of the furnace.

FIG. 3 also shows a sled beneath wheels on the furnace. The wheels andthe sled provide an advantage to the present furnace, in that they allowfor easy tilting and maneuvering of the furnace. For example, the sledmay be used to tilt the furnace in order to lower the amount of timenecessary to drain the furnace. In addition, the wheels and the sledallow the furnace to be moved from location to location with ease. As anexample, the wheels may be used in conjunction with a track to move thefurnace to or from a trailer truck, a land-based building, or a ship.Thus, the present disclosure relates, in some embodiments, to a portablefurnace not previously present in the art.

FIG. 4 is a cross-section view of the front of the furnace mounted on astand in an operational format, according to one embodiment.

In the embodiment shown in FIG. 4, a mobile overhead crane 23 is used tolower new electrode segments into position to remove the furnace crownto facilitate changing of the refractory ceramic blocks.

The embodiment shown in FIG. 4 provides a beneficial arrangement andillustrates the presence and use of a caster unit 24 that is configuredto and that facilitates pour-off and collection of the molten metal.When the furnace is used for steel production, this provides a method ofcasting steel slabs and ingots.

Operation of the furnace may be, for example, in a three-story building,with the second and third stories being clearstory. This could eliminatethe need for a caster well and facilitate movement of the casters.Alternatively, the furnace may be used in a two-story building.

However, the furnace described herein may be made so as to achievepreviously unknown space savings. The furnace arrangement discussedherein, in addition to the high organic content of the processedmaterial, means that the furnace may be constructed in a two-storyconfiguration, i.e., two stories tall, whereas previous furnaces wererequired to be three stories tall or higher.

FIG. 5 is a cut-away side view of the furnace, expanded from FIG. 4, inan operating position within the framework of a mobile overhead crane.

In the embodiment of FIG. 5, the furnace has been mounted on a sled witha canted end, allowing the furnace to be lifted and tilted toward theemptying ports to facilitate complete removal of the slag and/or moltenmetal to service the furnace, which may include replacing the refractoryceramic blocks. A crane used for such an operation will need to havesufficient lifting capacity, and may require a crane with, for example,at least 27 tons of lifting capacity.

In certain embodiments, the furnace may be manipulated and moved in allthree dimensions, thereby permitting controlled placement of theelectrodes in relation to the slag layer and the molten metal layer, aswell as controlled placement of the loading and unloading ports in thefurnace. For example, the furnace may be tilted to a predetermined angleto provide for the drainage of the furnace to allow for maintenance. Incertain embodiments, nitrogen may be used to cool the furnace prior tomaintenance or after a processing run. As another example of moving thefurnace, the furnace may be tilted to a predetermined angle to permitthe selective removal of slag, metal, or a particular metal in themolten metal layer.

FIG. 6 is a cross-section of an example system used to inject steam justbelow the surface of the slag bath.

In the embodiment shown in FIG. 6, the four tubular projections 11 arethe main steam feeders, and pass through an outer surface of thefurnace, which may include steel plates 25. The tubular projections 11are then shown entering an inner hollow co-plate section 26 of thefurnace.

The steam fills this hollow section and enters the slag bath throughchannels in each refractory ceramic block at a point below the uppersurface of the slag bath. This provides for uniform feeding of the steamand breakdown of the water molecules. Convections in the slag bathdistribute the free oxygen for maximum coupling with individual carbonatoms, thereby forming carbon monoxide.

FIG. 7 illustrates example mechanisms used to control the utilization,operating angle and spacing of the functional electrodes.

The system illustrated in FIG. 7 controls utilization and operatingangle via air pressure. Although such control could also be accomplishedwith mechanical devices, it is believed that the air pressure system ismore reliable and is less affected by the heat generated by the furnace.Electrode spacing is determined mechanically and may be determined basedon the needs of the feedstock. The electrodes may be moved in vertical,horizontal, or angled directions to, for example, customize the shapeand location of the plasma arc in the furnace or to control thetemperature and current in the slag bath.

FIG. 7 shows a T-fitting 27 containing an actuator valve, located inFIG. 7 to the left of the electrode 28, which allows for differentialair pressures between the upper and lower control mechanisms 29 and 30.Air enters the furnace through the T-fitting 27. Here, it is noted thatthe electrode could be either a functional electrode or a non-functionalelectrode, such as a backboard electrode. An air pressure outlet 31feeds through the upper mounting plate 32 on the right side of theelectrode 28 and affects the lower control unit on that side.

The crosshatched devices 33 in the upper control unit are in contactwith the electrode and are differentially compressible. In certainembodiments, transformers and rectifiers may be present in crosshatcheddevices 33. Compression in this embodiment is accomplished by applyingpressure to move a steel plate 34 against the outer surface of the unit.The interior side of the lower control unit 30 is composed of asimilarly compressible material that is in contact with a collar 35surrounding the electrode. The collar 35 may be made from, for example,polished steel or titanium. Air pressure is developed inside a chamber,putting pressure on the surface of the electrode collar 35. If desired,the air pressure may be applied such that the electrode moves downwardby gravity feed as it is consumed at its operating tip. Sensors, whichmay be located in the collar 35, may monitor this movement and, via theuse of appropriate software, notify the operator when a new electrodesegment is required. The rate of deterioration is affected by factorssuch as the operating temperature, whether they are submerged in theslag, and the amount of water in the material being processed. Incertain embodiments, a new section of electrode may be inserted once aweek.

At the base of the upper and lower control units 29 and 30 in thisembodiment are a pair of slide plates 36 mounted in guides above andbelow the sides of a channel in the steel shell of the furnace crown. Inthe embodiment shown, the slide plates 36 have a circular opening equalto the diameter of the electrode plus its collar, forming an airtightseal between the electrode 28 and the upper and lower slide plates. Inother embodiments, the slide plates 36 have a shape so as to provide foran airtight seal between the electrode 28 and the upper and lower slideplates. In embodiments in which there are two functional electrodes, thedistance between the electrodes may be adjusted by moving the slideplates 36 to a desired position, for example to the left or right, andlocking them in place.

The operating angle of the electrodes in the furnace may be controlledvia a sensor, which may be located in the actuator valve in theT-fitting 27. The sensor triggers air flow through the T-fitting thatwill result in increased or decreased pressure on one side of theelectrode. For example, decreased pressure on the left unit withincreased pressure on the right unit cants the electrode inward towardthe second electrode and the amount of differential pressure determinesthe angle. The compressible material on the electrode collar compensatesfor the differential pressure within the openings in the slide plates.

The furnace as described herein is capable of processing, and may beconfigured to process, the types of waste typically processed using DCplasma arc furnaces, including, for example, organic waste, inorganicwaste, and municipal solid waste. Such waste may include, for example,used tires or scrap steel as described herein. However, the furnace asdescribed herein is also configured so as to process large amounts ofmetal.

Inorganic and organic wastes may be processed at rates determined by theuser, including rates of 15 tons, 25, and up to 75 tons per hour ormore. For example, metal may be fed into the furnace at a rate of up to,for example, 25 tons per hour. Municipal solid waste may also beprocessed at a rate determined by the user, including a rate of, forexample, from 10 tons to up to 20 tons per hour. In another example,metal feedstock may be fed into the furnace at a rate of, for example,from 5-25 tons per hour, and in particular 5 tons, 10 tons, 15, tons, 20tons, or 25 tons per hour. In another example, non-metal feedstock maybe fed into the furnace at rates from, for example 15-75 tons per hour,and in particular, 15 tons, 25 tons, 35 tons, 45 tons, 55 tons, 65 tons,or 75 tons per hour. Higher rates may be used if the furnace isconfigured appropriately. The feed rates of the metal and non-metalfeedstocks may be tailored to take advantage of the energy benefitsobtained by using the non-metal feedstock as disclosed herein. Feedrates of municipal solid waste may be limited by the asymmetric natureof the municipal solid waste.

The output of the furnace herein may include electrical energy,compressed carbon dioxide, combustible gases having a clean andefficient ratio of hydrogen and carbon monoxide, construction aggregate,and pure steel, which may be formed into slabs or ingots. The output ofthe furnace may also include metal of various types as processed withinthe furnace, and in certain embodiments, the output may include metalingots or castors containing from, for example, 75%-100% of a singletype of metal (for example, gold or silver). In certain embodiments, themetal ingots or castors may contain at least 80%, or at least 90%, or atleast 95%, or at least 99%, or in some embodiments 100% of a single typeof metal, such as gold, silver, or platinum.

Another material that may be output from the furnace and methodsdescribed herein is silica sand or vitrified frit. Such material hashigh value in construction because it is resistant to freeze/thawcycles. Thus, the use of these materials in roads and other structuresthat are exposed to heating and cooling cycles serves to extend the lifeof the roads or other structures.

Because of the compact nature of the furnace described herein, it ispossible to load such furnaces onto ships or barges to provide formobile metal processing centers, mobile power plants, or mobile wasteremoval systems. The compact size of the furnace means that in someembodiments, up to 20 or about 20 furnaces may be loaded onto a mediumsized container ship, or up to 10 or about 10 furnaces may be loadedonto a barge. The barge or container ship may be docked, with conveyorbelts running from the dock to each furnace. The conveyor belts maycarry the materials from the dock into each furnace. Conveyor belts orpower lines may be used to transport the end products from the furnacesback to the dock or other desired destination.

When a ship loaded with furnaces completes processing at onedestination, it may travel to a new destination and begin processingmaterials from the new destination. This is particularly advantageousfor those localities that wish to save space by not having dedicatedwaste removal facilities.

The compact nature of the furnace also means that one or more furnacesmay be conveyed from point to point via trucks. For example, a singlefurnace may be broken into components of sufficient size that threetrucks may be sufficient to transport a furnace from point to point.

In addition, the present disclosure envisions an emergency powergenerating station or metal processing center or waste removal systemfor areas hit by disasters, where those disasters may have hampered thatarea's ability to generate power, process metal, or remove or processwaste. A barge system such as described herein may be particularlybeneficial in areas that have been impacted by natural disasters such ashurricanes, as the barge may enter the area when safe and then aid inthe removal of debris and waste while generating electricity from thedebris and waste.

Example: Processing of Harbor Sediment

Harbor sediment was processed in a DC plasma arc furnace with theresults shown in Table 1:

TABLE 1 Amount Percent dissociated dissociated Untreated during duringcontent processing processing Item mg/g mg/sample mg/g % Acenaphtene0.15 0.406 0.012 92 Acenaphtylene 0.51 0.581 0.017 97 Anthracene 0.81.94 0.057 93 Benzo[a]anthracene 1.46 0.647 0.019 99 Benzo[a]pyrene 1.630.42 0.012 99 Benzo[b]fluoranthene 2.31 3.57 0.104 95Benzo[g,h,i]perylene 1.03 2.71 0.079 92 Benzo[k]fluoranthene 0.72 0.420.012 98 Chrysene 1.63 1.3 0.038 98 Dibenzo[a,h]anthracene 0.3 0.070.002 99 Fluoranthene 2.95 10.1 0.295 90 Fluorene 0.22 0.54 0,016 93Indeno[1,2,3-cd]pyrene 1.12 0.481 0.014 99 Naphthalene 0.31 37.1 1.082−249 Phenantrene 1.29 30.3 0.884 31 Pyrene 2.69 4.28 0.125 95

In Table 1, the untreated content reflects the amount of each listedmaterial present in the harbor sediment that was tested. Bricks of theslag layer were tested to determine the amount of each materialdissociated in the furnace. Without wishing to be bound by theory, it ishypothesized that the increased naphthalene content is a result of otherlisted compounds breaking down to form naphthalene. The un-dissociatedmaterials were encapsulated and fixated in the slag. The un-dissociatedmaterials were non-leachable.

For the data in Table 1, sewage sludge was added to the furnace togetherwith the harbor sediment.

Hence, Table 1 illustrates that certain embodiments of the presentdisclosure may be used to process harbor sediment.

Even though certain specific embodiments are thoroughly described in thepresent application, it should be understood that the same conceptsdisclosed with respect to those specific embodiments are also applicableto other embodiments. Furthermore, individual elements of the furnaceand methods disclosed herein are described with reference to particularembodiments only for the sake of convenience. It should be understoodthat individual elements of the furnace and methods disclosed herein areapplicable to embodiments other than the specific embodiments in whichthey are described.

In addition, it should be understood that the scope of the presentdisclosure is not limited to the above-described embodiments, and thoseskilled in the art will appreciate that various modifications andalterations are possible without departing from the scope of the presentdisclosure.

What is claimed is:
 1. A method of processing metal in a DC plasma arcfurnace, comprising: feeding nitrogen gas into the furnace; maintainingan anoxic gas atmosphere within the DC plasma arc furnace; providing atleast one nitrogen plasma arc between at least two electrodes in thefurnace; feeding a metal feedstock into at least one of the at least onenitrogen plasma arcs in the DC plasma arc furnace; feeding a non-metalfeedstock into at least one of the at least one nitrogen plasma arcs inthe DC plasma arc furnace and maintaining a temperature of the DC plasmaarc furnace at a temperature of at least 2,500° C. during the feeding ofthe metal feedstock and the feeding of the non-metal feedstock; whereinthe metal feedstock and the non-metal feedstock are processed at thesame time in the furnace, and wherein the furnace comprises refractoryblocks sufficient to withstand temperatures of at least 2,500° C.
 2. Themethod according to claim 1, wherein the non-metal feedstock comprisesone or more items selected from the group consisting of waste materials,municipal solid waste, iron ore, radioactive material, and organicmaterial.
 3. The method according to claim 1, wherein the non-metalfeedstock comprises from 0% to less than 50% metal.
 4. The methodaccording to claim 2, wherein the non-metal feedstock comprises one ormore items selected from the group consisting of municipal solid waste,industrial or household waste chemicals, chemical weapons, medicalwaste, radioactive material, infectious or otherwise biologicallyhazardous materials, human or animal sewage, soils or marine sedimentsexcavated or dredged from contaminated sites, recovered waste materialexcavated from landfills, used tires, used oil filters, vegetable orpetroleum based oils, oil bearing shale, and high sulfur coal.
 5. Themethod according to claim 1, wherein the non-metal feedstock is 65-100%organic.
 6. The method according to claim 1, wherein the metal feedstockcomprises at least 50% metal.
 7. The method according to claim 1,wherein the total feedstock fed into the furnace, not including themetal feedstock, is at least 65% organic.
 8. The method according toclaim 7, wherein the total feedstock fed into the furnace, not includingthe metal feedstock, is at least 75% organic.
 9. The method according toclaim 1, wherein the non-metal feedstock comprises municipal solid wasteand either (1) pelletized sewage sludge; (2) pelletized harbor sediment;or (3) quartered tires, or any combination of (1), (2), and (3).
 10. Themethod according to claim 1, comprising feeding the metal feedstock intothe furnace at a different entry point than the non-metal feedstock. 11.The method according to claim 1, comprising feeding at least one of thenon-metal feedstock or the metal feedstock into the furnace via ahollow-core electrode.
 12. The method according to claim 1, wherein thenon-metal feedstock comprises municipal solid waste and/or tires, andwherein the method comprises feeding the municipal solid waste and/ortires into the furnace by bouncing them off of a backboard electrode.13. The method according to claim 1, comprising forming a slag bathlayer comprising non-metallic materials and/or minerals in the furnace.14. The method according to claim 1, comprising forming a molten metallayer in the furnace.
 15. The method according to claim 14, comprisingmaintaining the metal layer to be 18-48 inches thick.
 16. The methodaccording to claim 1, wherein the metal feedstock comprises ferrous andnon-ferrous metals.
 17. The method according to claim 1, comprisingmoving electrodes horizontally or angularly while feedstock is beingprocessed in the furnace.
 18. The method according to claim 1,comprising testing at least one of the metal feedstock or non-metalfeedstock prior to its entry into the furnace by using at least one itemselected from the group consisting of a titrater, a moisture meter,magnetometer, oven, mass spectrometer, gas spectrometer, Geiger counter,an FTIR spectrometer, a Raman spectrometer, a thermogravimetricanalyzer, a differential scanning calorimeter, an NMR spectrometer, ascanning electron microscope, and an energy dispersive X-ray analyzer.19. The method according to claim 1, wherein the step of maintaining atemperature of the DC plasma arc furnace maintains a temperature of atleast 4,000° C. during the feeding of the metal feedstock and thefeeding of the non-metal feedstock.